Field of the Invention
The present invention relates to a magnetic tape and a magnetic signal reproducing device.
Discussion of the Background
Magnetic recording media include tape-shaped media and disk-shaped media. Magnetic recording media in the form of tapes, that is, magnetic tapes, are primarily employed in storage applications such as data-backup tapes. A signal is normally recorded on and reproduced from a magnetic tape by running the magnetic tape in a drive to bring the surface of the magnetic layer into contact with (cause it to slide over) a magnetic head (also referred to hereinafter simply as a “head”). However, with repeated running in a state of a high coefficient of friction during sliding of the surface of the magnetic layer over the head, the surface of the magnetic layer ends up being shaved, producing shavings. Such shavings may cause fluctuation in output (spacing loss), and with repeated running, compromise electromagnetic characteristics. Accordingly, it is desirable to increase the running durability of the magnetic tape (inhibit shaving of the surface of the magnetic layer with repeated running) to inhibit the drop in electromagnetic characteristics due to repeated running.
Conventional means of lowering the coefficient of friction include incorporating a lubricant into a magnetic layer provided on a nonmagnetic support or into a nonmagnetic layer provided between the magnetic layer and the nonmagnetic support (see Japanese Unexamined Patent Publication (KOKAI) No. 2004-273070, which is expressly incorporated herein by reference in its entirety) and incorporating a lubricant into a backcoat layer positioned on the opposite side of the nonmagnetic support from the magnetic layer (see Japanese Unexamined Patent Publication (KOKAI) No. 2006-31805, which is expressly incorporated herein by reference in its entirety).
As regards electromagnetic characteristics, Japanese Unexamined Patent Publication (KOKAI) No. 2004-273070 states that the signal-to-noise ratio (SNR) decreases when the distribution of indentations greater than or equal to 20 nm in depth on the surface of the magnetic layer exceeds 30/(175 μm×130 μm) (see Japanese Unexamined Patent Publication (KOKAI) No. 2004-273070, paragraph 0112).